Author Topic: Want to build a gas fired deck oven. Any plans available and suggestions?  (Read 33198 times)

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Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #150 on: August 30, 2012, 01:00:20 AM »
That design is choked up....additional gas inlet port recommended....plus, need to open up more flame holes if you ever want to see some btu's...
"Care Free Highway...let me slip away on you"


scott123

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #151 on: August 30, 2012, 01:17:25 AM »
Richard, is this home gas pressure or work gas pressure?

Do you have a reliable gauge for measuring the pressure?

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #152 on: August 30, 2012, 01:19:03 AM »
Don makes some good points about the length of the run and pressure. I'm recommending double the holes based upon the tight hole formation in weber grill burners and the ability of those burners to stay lit.  If you have the pressure, then I'd say drill out more holes.

Heat accelerates oxidation/rusting in steel, so theoretically, very thin steel plate might rust faster in the deflector role you're considering for it.  I believe 'aluminized steel' is made to counteract that.  This being said, I really don't see 1/8" or thicker steel ever rusting through at these temps. Any good design should give you burner access, so, with that access, you should be able to check deflector wear as well. If you do see any rust, go with ss next time. For now, though, I think you'll be perfectly fine with regular steel.

I don't think I've got enough pressure to double the total aperture of the ports.  The gas comes in 25Kg cylinders that they tell me is high pressure.  Its a little more than my home gas but not a lot.   Maybe I could double the number of holes but make the new one 1mm instead of 2mm?

The reason I liked aluminium was to spread the heat.  I know that's what 'deflectors' are for but I want to really spread the heat evenly.

The possibilities for a stone hearth are limited.  Fire bricks look like the best option atm.   On closer examination of the imported 9"x9" ones available I found out they are 2.5" thick.  As there will be about 20 separate bricks for the hearth I want them to be heating up at the same rate (trying to avoid hot spots).   Therefore aluminum looked good.

I'm now thinking along the lines of:  3mm steel plate, topped with 6mm aluminum, topped with the fire bricks.  Overkill on thermal mass but ........     The other thing I have been thinking is to make the surface of the aluminum act like a stone, i.e. rough it up: and use that as the hearth.   Aluminum is not very hard and causes Parkinsons Disease.   So maybe steel aluminum steel sandwich and rough the top layer of the steel up.   Just thoughts!

More holes is a good thing...they should stager at an advantageous/opposing angle though. Still gonna need fuel coming in at the a$$ end ..too long of a run no matter how much psi you present on the front end..IMHO of course..

Like the idea of staggering them - make sense.

In you're next post Bob, you saay choked up.   The control systems I'm looking at all have a blower to pump air into the burner.   Should sort it out.   Just don't really like the look of my burner after having seen the weber with millions of holes burning perfectly evenly!!

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #153 on: August 30, 2012, 01:28:49 AM »
Gas pressure
Home              27lbs/sq in
25Kg cylinder   33 lbs/sq in
Could increase the pressure to about 50 lbs/sq in if I talk to the supplyer and get them to put a different head on the cylinder.

Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #154 on: August 30, 2012, 01:42:57 AM »
pics are already showing pressure flame out...
"Care Free Highway...let me slip away on you"

scott123

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #155 on: August 30, 2012, 02:55:08 AM »
Richard, Marsal seems to possess pretty strong deflection kung fu.  The deflectors might be bent in some manner, perhaps to provide rigidity/stability and also better deflection. I have to admit, a flat 3 mm steel plate might not give you that level of even heating.

Steel + firebrick + H shaped burner should go a long way in giving you an evenly heated hearth. According this page

http://www.ehow.com/how_5761350_soften-aluminum-plate.html

Aluminum anneals at 700.  For you to reach a hearth of 650, the aluminum closer to the burner will most likely end up in the 800 realm, even if above steel. I would go with 6 mm steel and see where that gets you.  The conductivity and thickness should go a long way in evening out the heat.

27 psi is more than enough for a 200K btu banjo burner, but, perhaps the lengths of the runs are impacting the BTUs here. I'm not really sure how they should, though.  Regardless, if you can get 50, get 50.

If you do add holes, I would stick to holes of the same size, but I like Don's idea of a greater concentration of holes at the extremities. First see what it will do with 50 psi, though.  
« Last Edit: August 30, 2012, 03:00:29 AM by scott123 »

Offline lennyk

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #156 on: August 30, 2012, 04:39:30 AM »
Can you use an adjustable regulator ?
Here in Trinidad the common regulator is simply a snap on head to the tank and the switch basically presses down the release pin in the tank a fixed distance, however you can get regulators which don't use a switch but a knob which turns and can move the pin further than the switch type regulators.

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #157 on: August 30, 2012, 07:38:27 AM »
Richard, I meant LP for liquid propane,NG for natural gas. You didn't answer my question. Which size jet/orifice did you use, a smaller propane hole size or a larger natural gas orifice size? They are not interchangable. I have more but it seems important parts of posts are not being addressed.
Don

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #158 on: August 30, 2012, 07:45:40 AM »
Bob, Yes that is exactly what I am talking about. A certain diameter tube with a certain about of burner holes will only be capable of carrying a certain amount of gas. Which gives you more volume of water given a certain pressure at the inlet, a water hose that is 1/2" in diameter or 1"? Notice I'm saying volume not pressure.
Don

I have heard where another gas inlet was added on to the opposite end when a pipe run was too long for the original single inlet to provide enough umph. Is this what you are referring to Don?

"or add a manifold that supplies gas along it's length."




buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #159 on: August 30, 2012, 08:10:07 AM »
Scott, Without an increase in tube diameter simply turning up the gas pressure will not result in better more even combustion. You will not get better results on a propane grill by switching to a high pressure regulator, the burner isn't designed for that.
Don

scott123

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #160 on: August 30, 2012, 08:22:07 AM »
Don, unless I've been misreading some of the comments on the LBE thread, the LBE burners seem to be PSI/regulator dependent.

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #161 on: August 30, 2012, 08:32:18 AM »
Scott, You will also see that the volume inside a high pressure burner is large for it's length. You can't run more pressure through a burner than it was designed for, hence my example of using a high pressure regulator on a low pressure gas grill. One needs volume and pressure, not just pressure alone.
Don


Don, unless I've been misreading some of the comments on the LBE thread, the LBE burners seem to be PSI/regulator dependent.

scott123

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #162 on: August 30, 2012, 08:37:07 AM »
I can see that, Don, but is this burner volumetrically challenged?

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #163 on: August 30, 2012, 09:07:39 AM »
Richard, Marsal seems to possess pretty strong deflection kung fu.  The deflectors might be bent in some manner, perhaps to provide rigidity/stability and also better deflection. I have to admit, a flat 3 mm steel plate might not give you that level of even heating.

Steel + firebrick + H shaped burner should go a long way in giving you an evenly heated hearth. According this page

http://www.ehow.com/how_5761350_soften-aluminum-plate.html

Aluminum anneals at 700.  For you to reach a hearth of 650, the aluminum closer to the burner will most likely end up in the 800 realm, even if above steel. I would go with 6 mm steel and see where that gets you.  The conductivity and thickness should go a long way in evening out the heat.

27 psi is more than enough for a 200K btu banjo burner, but, perhaps the lengths of the runs are impacting the BTUs here. I'm not really sure how they should, though.  Regardless, if you can get 50, get 50.

If you do add holes, I would stick to holes of the same size, but I like Don's idea of a greater concentration of holes at the extremities. First see what it will do with 50 psi, though.  

Scott are you sure you posted the right link.  I couldn't find anything pertaining to even hearth heat.  

I also think I may have caused some confusion interchanging the words 'deflector' and 'plate'.   For clarity I've been thinking of sheet of metal to completely cover the 4'x2.5' hearth area.   The bent deflectors that Marsal use would be good if the refractory bricks were joined so the heat can travel by conduction from one end to the other.   Using small 9"x9" bricks makes it imperative that I even out the heat before it hits the bottom of the bricks.

The link you provided does talk about aluminium warping at fairly low temperatures so unless its bonded to steel I guess it's not going to be usable.

 

Hi Lenny.  Yes, we have the same type here but someone has told me that the pressure is already regulated by the head that the gas bottle comes with.  If I get that changed by the supplier I can get more pressure.


Richard, I meant LP for liquid propane,NG for natural gas. You didn't answer my question. Which size jet/orifice did you use, a smaller propane hole size or a larger natural gas orifice size? They are not interchangable. I have more but it seems important parts of posts are not being addressed.
Don

 Don.  I'm using LPG (liquid petroleum gas) and the venturi jet size is also 2mm, same as the ports on the burner.


I can see that, Don, but is this burner volumetrically challenged?

I'm guessing I wont know that until I've tested it with the blower attachment (blows air into the gas supply line) that is a standard attachment to the imported bread ovens here.
« Last Edit: August 30, 2012, 09:09:42 AM by Sqid »

scott123

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #164 on: August 30, 2012, 12:07:25 PM »
Don, I think I understand what you're saying.  I'm looking at the pipe size on the burner and seeing a diameter that would allow hundreds of thousands of BTUs of gas to pass, but this isn't about the diameter of the pipe, it's about the venturi.  The venturi is what dictates BTUs- at least, it does in this setting. It's not about pressure or pipe burner diameter or even about hole count, size or placement, but the venturi. Without a high BTU venturi, nothing can be done.

Is that correct, Don?
« Last Edit: August 30, 2012, 04:53:06 PM by scott123 »

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #165 on: August 30, 2012, 01:51:50 PM »
Richard, The standard hole sizes for LP gas and NG orifices are as follows: LP Gas Drill Size: #72 (.0250"), Natural Gas Drill Size: #56 (.0465"), your orifice/jet size is completly wrong, 2mm? that's way to big to be correct and there is no reason to continue discussing your burner until you have the proper sized jets installed.
Don

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #166 on: August 30, 2012, 02:03:06 PM »
 This is insanity to be suggesting that Richard use a high pressure burner system as it uses much more gas than than low pressure and that's a fact. He wants an efficient low water column system. Water column is a means to measure low pressure systems, ten to eleven inches is what's required. I simply won't get on that high pressure burner train.
Don







Offline lennyk

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #167 on: August 30, 2012, 04:34:11 PM »
what kind of air/oxygen intake does that burner have ?
it may be the limiting factor regardless of number holes and pressure.

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #168 on: August 30, 2012, 05:53:51 PM »
This is insanity to be suggesting that Richard use a high pressure burner system as it uses much more gas than than low pressure and that's a fact. He wants an efficient low water column system. Water column is a means to measure low pressure systems, ten to eleven inches is what's required. I simply won't get on that high pressure burner train.
Don


Aw Don  -  I measured the orifice size with my daughters ruler.   Could be 1.8mm or even 1.6mm.  I was wearing my crappy classes at the time  ::).  Drill size anywhere from 46 to 52.

For the amount of pressure in the cylinders I asked another one of my handy men.  He reckons about 32-35 psi.   Extrapolating the tables here http://www.joppaglass.com/burner/highp_chart.html  it could be about right if I'm aiming for about 150000 Btus.

10-11" water pressure equates to less than 1/2psi. ???  Seems very low and certainly difficult to get a lot of Btus.  Then again I guess the average kitchen gas cooker isn't using so much.

Anyway its a bit of a mute point because if I want the larger tanks of LP they come with that pressure regulator.  I don't really want the supplier having to do something special for me otherwise the running costs will go up.


Lenny = I've mentioned that the system I will be using will have a fan attachment to deliver more air to venturi.   Don't know, how much more, as I haven't bought it yet.   But it should be able to bump up the Btus.   It should also take care of the choking that Bob mentioned in an earlier post.
« Last Edit: August 30, 2012, 10:14:54 PM by Sqid »

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #169 on: August 31, 2012, 08:42:26 AM »
Richard,  You can not combine a forced air and a venturi burner system. In a venturi the vacuum created by the rush of gas out of the jet pulls air into the venturi area to be mixed. A forced air system is the exact opposite, it is the rush of air that pulls gas into the flow. The principles and execution are 180 degrees out from one another. Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.
Don
p.s. Richard, I went back and reread your posts and can't find a mention of using forced air until yesterday.
« Last Edit: August 31, 2012, 10:51:07 AM by buceriasdon »

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #170 on: August 31, 2012, 12:33:56 PM »
Richard,  You can not combine a forced air and a venturi burner system.

Good point Don.  Guess i shall have to stop dreaming about beautifully engineered and compact Weber burners if I'm going down the blower route.  Thanks for that!


Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.

No idea if there is one Don.  All I knew about high pressure vs low pressure a couple of months ago was that I needed a high pressure regulator if I wanted a gas bottle larger than 15Kg.  When I connect the gas bottle to my oven I do turn down the regulator to a minimum flow before I light it.  I then increase the flow ever so slightly to get a better flame.  Could well be using 'low pressure' pressure!

p.s. Richard, I went back and reread your posts and can't find a mention of using forced air until yesterday.

That's because I only mentioned it yesterday!  I had no idea until I was sourcing a control system that my oven was fitted with one.  Sorry for the confusion.
« Last Edit: August 31, 2012, 12:44:10 PM by Sqid »

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #171 on: August 31, 2012, 04:15:39 PM »
Richard, I find it impossible to believe you can't locate a low pressure regulator there. That's absurd, all LPG tanks are high pressure at it's outlet everywhere in the world and they all can be brought down in pressure! I've stated this before and I'll say it again, you don't want high pressure! You want to ignore my recommendations, fine, I'm tired of repeating myself over and over. Best of luck with whatever.
Don

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #172 on: August 31, 2012, 11:29:02 PM »
Richard, I find it impossible to believe you can't locate a low pressure regulator there. That's absurd, all LPG tanks are high pressure at it's outlet everywhere in the world and they all can be brought down in pressure! I've stated this before and I'll say it again, you don't want high pressure! You want to ignore my recommendations, fine, I'm tired of repeating myself over and over. Best of luck with whatever.
Don

I shall ask again if there is a low pressure large gas bottle supplier.  But I don't see it as a big deal - with a regulator I can reduce the pressure to what I need and the gas bottles are proven to work on the many ovens here.

Exactly, which of your recommendations am I ignoring Don?
« Last Edit: August 31, 2012, 11:31:24 PM by Sqid »

Offline Jet_deck

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #173 on: August 31, 2012, 11:53:13 PM »
Richard,  You can not combine a forced air and a venturi burner system. In a venturi the vacuum created by the rush of gas out of the jet pulls air into the venturi area to be mixed. A forced air system is the exact opposite, it is the rush of air that pulls gas into the flow. The principles and execution are 180 degrees out from one another. Also could someone please show me a link to a high pressure commericial oven, I don't seem to be able to locate one on the internet.
Don
p.s. Richard, I went back and reread your posts and can't find a mention of using forced air until yesterday.

Don is 100% correct.  Show me one forced air venturi (or gas meeting ambient air mixing system). None. You are going to kill yourelf and some of your workers/customers if you don't shape up.  I am out.
Her mind is Tiffany-twisted, she got the Mercedes bends

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #174 on: September 01, 2012, 01:38:19 AM »
Don is 100% correct.  Show me one forced air venturi (or gas meeting ambient air mixing system). None.

Agreed Gene as  of a few posts ago:
Good point Don.  Guess i shall have to stop dreaming about beautifully engineered and compact Weber burners if I'm going down the blower route.  Thanks for that!



You are going to kill yourelf and some of your workers/customers if you don't shape up. 
Rather morbid Gene.   Lighten up!